Editor code: tidy up BOOLs,NULLs and overrides pt2.

Merge pull request #2873 from nemerle/tidy_up_editor_code_a_bit_split2

Code/Editor/Plugins/ComponentEntityEditorPlugin/SandboxIntegration.cpp

@@ -1816,7 +1816,7 @@ void SandboxIntegrationManager::ContextMenu_PushEntitiesToSlice(AzToolsFramework
     (void)targetAncestorId;
     (void)affectEntireHierarchy;
 
-    AZ::SerializeContext* serializeContext = NULL;
+    AZ::SerializeContext* serializeContext = nullptr;
     EBUS_EVENT_RESULT(serializeContext, AZ::ComponentApplicationBus, GetSerializeContext);
     AZ_Assert(serializeContext, "No serialize context");